P992: OUTCOMES OF GLOBAL COAGULATION ASSAYS IN PATIENTS WITH PHILADELPHIA-NEGATIVE MYELOPROLIFERATIVE NEOPLASMS WITH RESPECT TO THEIR CLINICAL AND GENETIC DETERMINANTS OF CLONAL EVOLUTION
Authors: A. Lucchesi, R. Napolitano, M. T. Bochicchio, G. Simonetti, G. Micucci, M. Poggiaspalla, V. Di Battista, G. Musuraca, F. Foca, G. Giordano, L. Catani, M. Napolitano
Journal: HemaSphere (2022)

Background: Classical Myeloproliferative Neoplasms (MPNs) are hematopoietic stem cell diseases characterized by inflammation, promotion of atherosclerosis, hypercoagulability, fibrosis, and clonal evolution. Our previous studies in cytofluorimetry have shown that the reduced expression of platelet fibrinogen receptor (PFR) - common to all MPNs - can be due to the hyperactivation of plasma-dependent mechanisms, such as tissue factor (TF) release, an unbalanced thrombin generation and the marked involvement of Protease Activated Receptors (PARs) and their signaling crosstalk with TGF-ß. Acetylsalicylic acid (ASA) seemed to be able to restore the expression of PFRs. Aims: The aim of the present study is to verify the existence of imbalances in hemostatic function in rotational thromboelastometry (ROTEM), with respect to the different classical forms of MPN, their cell counts, the presence of genetic mutations in Next Generation Sequencing (NGS), PFR expression, the use of ASA and the history of vascular events. Methods: We enrolled 53 patients affected by MPNs, naïve from any therapy, with the only exception of ASA (taken by 50% of patients). We used the samples to run assays of genetics (30-gene panel in NGS - SOPHiA Myeloid Solution™, SOPHiA Genetics, Switzerland), cytofluorimetric determination of PFRs, global coagulation by rotational tromboelastometry (ROTEM® Delta, Werfen, Spain) for INTEM, EXTEM, FIBTEM parameters. Results: ROTEM parameters appear to exhibit substantial variations, depending on the type of disease under investigation, cell counts, and selected mutations. Since most of the values are in the normal range, the results should be read in terms of “efficiency” or “preferential use” of one pathway over another. In particular, essential thrombocythemia (ET) and CALR mutation seem to be related to an increased efficiency of both classical coagulation pathways, with significantly more contracted clot formation times (CFT). In contrast, primary myelofibrosis (PMF) and polycythemia vera (PV) show greater imbalances in the hemostatic system. PV patients have longer CFT (EXTEM 114 sec, p= 0.008, INTEM 82 sec, p=0.027) and at the same time a selective contraction of the parameters in INTEM for higher platelet (Plt), white blood cells (WBC) and hemoglobin (Hb) levels. PMF - on the contrary - seems to exploit more the extrinsic pathway (EXTEM) - figure A-B. In multivariate analysis, the major contribution to the alterations is credited to Hb values for PV, while only Plt retains statistical significance for PMF and ET. Selected mutations are associated with changes in ROTEM parameters. Among the DTA mutations, the presence of DNMT3A shows a significant reduction in clotting time (CT) in EXTEM, while ASXL1 is associated with reduced maximum lysis (ML). EZH2 could be responsible for CFT elongations in the INTEM assay. In addition, increased expression of PFRs is associated with bleeding history and sustained CT time at FIBTEM under ASA prophylaxis. Image:Summary/Conclusion: In the most indolent MPNs (such as ET, especially if CALR mutated) the balance and efficiency of the classical pathways is preserved. In PMF, the hemostatic system is unbalanced towards the extrinsic pathway, confirming the connection between increasing fibrosis and plasma-dependent hypercoagulable states. In contrast, rheological characteristics and endothelial stress in PV seem to result in a greater involvement of the intrinsic pathway. ROTEM and PFR expression confirm the existence of dynamic states of hypercoagulability in MPNs and could be used to assess the efficacy of prophylaxis.